Do all tidal effects vanish in the limit where GR reduces to SR? I'm an amateur studying General Relativity (GR). A basic question on which I'm still unclear is the sense in which GR reduces to Special Relativity (SR) in the limit.  I understand that the laws of SR apply locally, as Euclidean laws apply locally on the surface of the earth. But am I wrong that tidal effects will not vanish in this way?  Roughly speaking, won't the ratio of tidal acceleration to the size of a test region, $r$, not converge to $0$, as $r$ approaches $0$? 
 A: The answer to this question, is similar to the equivalence principle
The Equivalence Principle
The Equivalence Principle

For a small enough system, there is no difference between a
gravitational field and uniform acceleration.

Note the equivalence principle as given by Einstein doesn't talk of the sizes of the system, the one stated above is the modified statement, which shows that the two situations aren't exactly the same.
But we know this doesn't hold good if the system in consideration is big enough, for example a one-mile man near the surface of Earth experiences significant tidal forces that stretch and squeeze him.

Curvature and Tidal Forces
The logic behind gravity being related to curvature is tidal effects as stated by Prof.Leonard Susskind in his lectures. Consider a two dimensional world, if we somehow manage to add curvature to the surface, and if the flatland creature tries to get on the curved part, it has to stretch/squeeze. In other words it experiences tidal forces.

Tidal Forces
The amount of tidal forces the creature of flatland experiences on moving to the curved surface doesn't depend only on how much the space is curved, it also depends on the size, something which you could intuitively guess from the Equivalence Principle. Despite the curvature being invariant of the scale, tidal forces are not the same.
Also, when GR can be approximated to SR, it essentially means that the curvature of Space Time is very less, and that means that the tidal effects begin to disappear.
